所有字母最终都会变成C，所以只要看第一个字母就行

#include <iostream>
#include <string>
using namespace std;
int main()
{
string str;
cin >> str;
switch(str[0])
{
case 'A': cout << "Aquaman Win" << endl; break;
case 'B': cout << "Superman Win" << endl; break;
case 'C': cout << "Batman Win" << endl; break;
}
return 0;
}

#include <iostream>
#include <string>
using namespace std;
int main()
{
string str;
cin >> str;
switch(str[0])
{
case 'A': cout << "Aquaman Win" << endl; break;
case 'B': cout << "Superman Win" << endl; break;
case 'C': cout << "Batman Win" << endl; break;
}
return 0;
}